COMMUNITY FORUM

raising and insulating a new floor

I want to lay a new cottage floor over an older porch floor, and at the same time raise the level 1-1/2" to align with adjacent room. The old floor is quite solid, smooth and moisture-free. Is there an insulating type board of approx 3/4" thick that I can simply lay down then fasten the new 3/4" plywood floor directly through it, without need of strapping? Do I need VB?